The invention relates to apparatus for the handling and/or treatment of particulate materials. Examples of particulate materials are sand, gypsum or cement and these may conveniently be treated using a fluidizing technique. The term "treatment" refers to such processes as heating, cooling, moistening or drying.
In an example of the treatment of particulate material according to the invention, foundry molding sand may have to, from time to time, be cooled so that it can continuously be recycled. It will be understood that the sand becomes heated as a result of contact with molten metal during molding operations, although such heating is not uniform. In order to successfully recycle the sand, it should be cooled to a fairly uniform level.
It has previously been considered whether it is possible to cool this sand by fluidization, but hitherto, attempts have met with only limited success. This is because clay-bonded molding sand from which the castings have been removed can vary widely in moisture content and contains a proportion of agglomerates in the form of chemically-bonded core sand and fragments of solidified metal. When such sand is therefore treated in a conventional horizontal fluidized bed, the bed is quickly rendered inoperative by clogging of the inlets for the fluidizing medium.
A further disadvantage arises where there is a wide range of particle size to be treated, since the velocity of the fluidizing medium required for large particles will be substantially greater than that for smaller particles. Thus when a sufficiently high velocity is reached for the larger particles, say 12 meters/minutes for 50.mu. particles, the smaller particles, say 10.mu., tend to be lost into the ambient area and present a severe dust problem besides loss of sand.
The invention sets out to alleviate the above problems.